Exemplary embodiments relate to a semiconductor memory device, and more particularly, relate to a data storage device including a non-volatile memory device.
Semiconductor memory devices may be classified as non-volatile memory devices and volatile memory devices. Non-volatile memory device retain data stored therein even when power is removed or off. Volatile memory devices support faster read and write operations, but data stored therein may be lost at power-off. The non-volatile memory devices may be used to store contents to be retained regardless of application of power. An example of a non-volatile memory device is a flash memory device, which may be more highly integrated than a typical electrically erasable programmable read-only memory (EEPROM), for example, so that it is suitable for auxiliary mass data storage.
Flash memory devices are increasingly used as storage media for replacing hard disk drives (HDDs), due to technological advances and reduced prices of the flash memory devices. Such a storage device may be referred to as a solid state drive (SSD) or a solid state disk. The SSD input and output data at high speeds, and mechanical delay and failure rates are typically low. Further advantages of the SSD include robust data storage against external impact, lower radiation, noise and power consumption, light weight and compactness. Also, the SSD does not use a mechanically rotating disk. Accordingly, demand for SSDs increases, particularly in wireless communications, which require storage having low power and large volume.
In general, a storage device includes volatile random access memory (RAM), such as dynamic random access memory (DRAM) or static random access memory (SRAM), as write buffer memory (or cache memory) between a host interface and flash memory. Using the volatile RAM as a write buffer minimizes the difference between an interface speed of the host and write speed of the flash memory device. Furthermore, the cache memory enables fast access to frequently accessed data. To this end, high speed volatile RAM is used as the write buffer memory (or cache memory), generally. However, data integrity may be compromised when power of the storage device is lost or otherwise removed while write data is written in the write buffer memory, but not yet written in the flash memory.